Ring buffer design

ABSTRACT

A system and method for managing data in a ring buffer is disclosed. The system includes a legacy ring buffer functioning as an on-chip ring buffer, a supplemental buffer for storing data in the ring buffer, a preload ring buffer that is on-chip and capable of receiving preload data from the supplemental buffer, a write controller that determines where to write data that is write requested by a write client of the ring buffer, and a read controller that controls a return of data to a read client pursuant to a read request to the ring buffer.

BACKGROUND

A ring buffer, also known as a circular buffer, circular queue, orcyclic buffer, is a data structure that uses a single, fixed-size bufferas if it were connected end-to-end. The ring buffer structure improvesthe buffering of data streams. Generally, a ring buffer does not need tohave its elements shuffled around when one is consumed. A ring buffer iswell-suited as a first-in first-out (FIFO) buffer.

Ring buffers may be designed to be on-chip or off-chip. On-chip ringbuffers exhibit fast write/read times but have limited size (e.g., oncethe size is consumed, on-chip ring buffers stall with no free space).Off-chip ring buffers have larger sizes but exhibit slower access speeddue to the use of a Layer 2 (L2) cache or off-chip memory to store data.

In operation, a ring buffer has a write and read pointer. A consequenceof the circular buffer is that when it is full and a subsequent write isperformed, then it starts overwriting the oldest data. A circular buffercan be implemented using pointers or indices for the buffer start inmemory, buffer end in memory, or buffer capacity, start of valid data,and end of valid data, or amount of data currently in the buffer.

When an element is written, the start pointer is incremented to the nextelement. In the pointer-based implementation strategy, the buffer's fullor empty state can be resolved from the start and end indexes. When thestart and end indexes are equal, the buffer is empty. When the startindex is one greater than the end index, the buffer is full.Alternatively, if the buffer is designed to track the number of insertedelements n, checking for emptiness means checking n=0 and checking forfullness means checking whether n equals the capacity.

Ring buffers are broadly used in ASIC design. Size and accessperformance are two major concerns to ring buffer design and use. Largersizes can decouple the data producer and the consumer, but at the costof access (read/write) speed and integrated circuit area. Therefore, aneed exists for an improved ring buffer design.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawingswherein:

FIG. 1 is a block diagram of an example device in which one or moredisclosed invention may be implemented;

FIG. 2 is an illustration of the structure of a ring buffer;

FIG. 3 illustrates the data write control flow of the ring buffer ofFIG. 2;

FIG. 4 illustrates another data write control flow of the ring buffer ofFIG. 2;

FIG. 5 illustrates a link list for descriptor tables and data in thering buffer of FIG. 2;

FIG. 6A illustrates method for updating the write data associatedmanagement information of the ring buffer of FIG. 2;

FIG. 6B illustrates the steps of updating the ring buffer map tableassociated with FIG. 6A;

FIG. 6C illustrates the steps of updating the legacy ring bufferdescriptor table associated with FIG. 6A;

FIG. 6D illustrates the steps of updating the L2 descriptor tableassociated with FIG. 6A;

FIG. 6E illustrates the steps of updating the preload ring bufferdescriptor table associated with FIG. 6A;

FIG. 7 illustrates management information update for write data of thering buffer of FIG. 2;

FIG. 8 illustrates the read control arbitor for the ring buffer of FIG.2;

FIG. 9 illustrates a read control arbitration finite state machine (FSM)to arbitrate the reads in the ring buffer of FIG. 2;

FIG. 10 illustrates the method of operations in state rd_state of FSM ofFIG. 9;

FIG. 11 illustrates management information extraction and update inrd_state;

FIG. 12 illustrates the operations in state pl_rd_state of the FSM ofFIG. 9;

FIG. 13 illustrates management information extraction and update inpl_rd_state;

FIG. 14 illustrates the operations in state lrb_rdat_return_state of theFSM of FIG. 9;

FIG. 15 illustrates the ring buffer most recent usable indexcalculation;

FIG. 16 illustrates the legacy ring buffer most recent usable indexcalculation;

FIG. 17 illustrates an example where current read index is betweencurrent write index and most recent usable index leavingcur_lrb_mru_indx unchanged;

FIG. 18 illustrates the operations in state plrb_rdata_return_state ofthe FSM of FIG. 9;

FIG. 19 illustrates the preload ring buffer most recent usable indexcalculation;

FIG. 20 illustrates an example where current read index equals the mostrecent usable index skipping all obsolete entries up to current writeindex;

FIG. 21 illustrates the operations in state l2_rdata_return_state of theFSM of FIG. 9;

FIG. 22 illustrates the L2 most recent usable index calculation; and

FIG. 23 illustrates an example where current read index equals the mostrecent usable index skipping all obsolete entries up to some usableentry.

DETAILED DESCRIPTION

The present disclosure is directed to an improved ring buffer designthat combines an on-chip ring buffer and a supplemental buffer that canbe a large sized buffer and can include off-chip storage. Hereinafter,the on-chip ring buffer is referred to as a “legacy ring buffer”.Examples of the off-chip storage include a main memory (e.g., DRAM,hereinafter referred to as “DDR”) or a L2 cache (hereinafter referred toas “L2 cache” or “L2 buffer”) for ring buffer data. This design providesthe advantages of on-chip ring buffer access times and the increasedsize of off-chip ring buffers.

As will be described in more detail below, a write controller isutilized to control data writes to the ring buffer, and a readcontroller is utilized to control data reads from the ring buffer. Fromdata write/read client viewpoint, the on-chip ring buffer and L2 cacheare combined as a flat ring buffer.

The present invention includes a hierarchical ring buffer structure andan efficient, low complexity de-allocate/allocate method for associatedbuffer management that improves ring buffer read/write rate performancewhile removing or reducing the size limitations. The present inventionmay be applied to a parameter cache, position buffer, local data share(LDS), or other device, within a graphics processing unit (GPU) chip,for example, and used as ring buffer.

According to an implementation, a system and method for managing data ina ring buffer is disclosed. The system includes a legacy ring bufferfunctioning as an on-chip ring buffer, a supplemental buffer for storingdata in the ring buffer, a preload ring buffer that is on-chip andcapable of receiving preload data from the supplemental buffer, a writecontroller that determines where to write data that is write requestedby a write client of the ring buffer, and a read controller thatcontrols a return of data to a read client pursuant to a read request tothe ring buffer.

The ring buffer operates such that if the legacy ring buffer is not fulland the supplemental buffer is empty, the write controller writes to thelegacy ring buffer on a write request. If the legacy ring buffer is fulland the supplemental buffer is not full, the write controller storesdata to the supplemental buffer on a write request. If the legacy ringbuffer is full and there is no data in the supplemental buffer, thewrite controller writes data to preload ring buffer on a write request.

The ring buffer operates such that upon receipt of the read request, theread controller examines the legacy ring buffer and preload ring bufferto satisfy the read request. If the legacy ring buffer contains the datato be read in the read request, the data is supplied from the legacyring buffer to satisfy the read request. If the preload ring buffercontains the data to be read in the read request, the data is suppliedfrom the preload ring buffer to satisfy the read request. If the legacyring buffer and preload ring buffer do not contain the data to be readin the read request, the data read request is sent to the supplementalbuffer to fetch the data. The system then returns the read data to theread client from the supplemental buffer.

FIG. 1 is a block diagram of an example device 100 in which one or moredisclosed embodiments may be implemented. The device 100 includes, forexample, a computer, a gaming device, a handheld device, a set-top box,a television, a mobile phone, or a tablet computer. The device 100includes a processor 102, a memory 104, a storage 106, one or more inputdevices 108, and one or more output devices 110. The device 100 may alsooptionally include an input driver 112 and an output driver 114. It isunderstood that the device 100 may include additional components notshown in FIG. 1.

The processor 102 includes a central processing unit (CPU), a graphicsprocessing unit (GPU), a CPU and GPU located on the same die, or one ormore processor cores, wherein each processor core is a CPU or a GPU. Thememory 104 is located on the same die as the processor 102, or islocated separately from the processor 102. The memory 104 includes avolatile or non-volatile memory, for example, random access memory(RAM), dynamic RAM, or a cache.

The storage 106 includes a fixed or removable storage, for example, ahard disk drive, a solid state drive, an optical disk, or a flash drive.The input devices 108 may include a keyboard, a keypad, a touch screen,a touch pad, a detector, a microphone, an accelerometer, a gyroscope, abiometric scanner, or a network connection (e.g., a wireless local areanetwork card for transmission and/or reception of wireless IEEE 802signals). The output devices 110 may include a display, a speaker, aprinter, a haptic feedback device, one or more lights, an antenna, or anetwork connection (e.g., a wireless local area network card fortransmission and/or reception of wireless IEEE 802 signals).

The input driver 112 communicates with the processor 102 and the inputdevices 108, and permits the processor 102 to receive input from theinput devices 108. The output driver 114 communicates with the processor102 and the output devices 110, and permits the processor 102 to sendoutput to the output devices 110. It is noted that the input driver 112and the output driver 114 are optional components, and that the device100 operates in the same manner if the input driver 112 and the outputdriver 114 are not present.

FIG. 2 is an illustration of the structure of a ring buffer 200. Ringbuffer 200 includes a descriptor table 210, a read controller 220, apreload ring buffer 230, a read control arbitor 240, a legacy ringbuffer 250, a L2 cache 260 and a write controller 270.

Legacy ring buffer 250 is an on-chip ring buffer and L2 cache 260 is alarge-size memory and may be off-chip memory. Preload ring buffer 230 isan on-chip ring buffer that preloads data from L2 cache 260. Writecontroller 270 controls data writes to ring buffer 200. Read controller220 controls read data from ring buffer 200. From a data write/readperspective, the legacy ring buffer 250 and L2 cache 260 are combined tooperate as if they are a flat ring buffer.

A data write request and data to be written are inputs to writecontroller 270. For example, the data write request may come from a GPUshader. As will be described in more detail below with respect to FIGS.3 and 4, write controller 270 writes to legacy ring buffer 250, preloadring buffer 230, or L2 cache 260.

Read control arbitor 240 is a part of read controller 220.Alternatively, the read control arbitor 240 may be placed or reside inanother part of ring buffer 200. Read control arbitor 240 functionsaccording to the flows of FIGS. 8 and 9. Read control arbitor 240 is inbidirectional communication with legacy ring buffer 250, L2 cache 260,and preload ring buffer 230. Read control arbitor 240 receives readrequests from a read client (not shown) and receives preload readrequest from read controller 220 via a decided preload condition.

Read controller 220 receives the data reads based on the control of readcontrol arbitor 240 from legacy ring buffer 250, L2 cache 260, andpreload ring buffer 230. The read controller 220 has a data read output.

Preload ring buffer 230 has as an input a data write from a data read ofL2 cache 260.

Descriptor table 210 communicates with write controller 270 and withread controller 220. In an implementation, the communications with thewrite controller 270 and read controller 220 are unidirectional. Inanother implementation the communications are bidirectional.

FIG. 3 illustrates the data write control flow 300 of the ring buffer200 of FIG. 2. Flow 300 controls the data write by deciding to write tolegacy ring buffer 250 and/or L2 cache 260.

At step 310, flow 300 begins with an initial/idle state to wait for awrite request. At step 320, a determination is made if the write requestfrom the write client is a write request to be written. If thisdetermination 320 is NO at block 325, flow 300 returns to step 310.

If the determination 320 is YES, then step 330 is performed to allowflow 300 to control when a write client stores data to ring buffer 200by deciding if the legacy ring buffer 250 is not full (i.e., hasavailable space for writing) and L2 cache 260 is empty. If decision 330is YES, the data write is directed to the legacy ring buffer 250 untilthe legacy ring buffer 250 is full at step 335.

If decision 330 is NO, then a determination at step 340 is made todecide if the legacy ring buffer 250 is full, i.e., when one data blockcannot be written, and L2 cache 260 is not full. If determination 340 isYES, the data write is directed to the L2 cache 260 at step 345.

If determination 340 is NO, a determination is made at step 350 todecide if the legacy ring buffer 250 free space exceeds a programmablewatermark and L2 cache 260 is not empty. If determination 350 is YES,the data write is directed to the legacy ring buffer 250 until legacyring buffer 250 is full at step 355.

If determination 350 is NO, a determination of whether L2 cache 260 isnot full is performed at step 360. If determination 360 is YES, the datawrite is directed to L2 cache 260 at step 365. If determination 360 isNO the write request may be stalled at step 375.

FIG. 4 illustrates another data write control flow 400 of the ringbuffer 200 of FIG. 2. Flow 400 is utilized when previous date write fromwrite client is written to preload ring buffer 230 to further decreaseL2 cache 260 accesses. That is, anytime there is no data in L2 cache 260and the preload ring buffer 230 is not full, the write controller 270writes data directly to preload ring buffer 230. More specifically, atstep 410, flow 400 begins with an initial or idle state to wait for awrite request. At step 420, a determination is made if the write requestfrom the write client is written. If this determination 420 is NO atblock 425, flow 400 returns to step 410.

If the determination 420 is YES, then step 430 is performed to allowflow 400 to control when a write client stores data to ring buffer 200by deciding if the legacy ring buffer 250 is not full and L2 cache 260is empty. If decision 430 is YES, the data write is directed to thelegacy ring buffer 250 until the legacy ring buffer 250 is full at step435.

If decision 430 is NO, then a determination at step 440 of whether thelegacy ring buffer 250 is full, L2 cache 260 is empty, and preload ringbuffer 230 is not full is made. If decision 440 is YES, the data writeis directed to the preload ring buffer 230 until the preload ring buffer230 is full at step 445.

If decision 440 is NO, then a determination at step 450 is made todecide if the legacy ring buffer 250 is full, i.e., when one data blockcannot be written, and L2 cache 260 is not full. If determination 450 isYES, the data write is directed to the L2 cache 260 at step 455.

If determination 450 is NO, a determination is made at step 460 todecide if the legacy ring buffer 250 free space exceeds a programmablewatermark and L2 cache 260 is not empty. If determination 460 is YES,the data write is directed to the legacy ring buffer 250 until legacyring buffer 250 is full at step 465.

If determination 460 is NO, a determination of whether L2 cache 260 isnot full may be performed at step 470. If determination 470 is YES, thedata write is directed to L2 cache 260 at step 475. If determination 470is NO the write request may be stalled at step 485.

FIG. 5 illustrates a link list 500 for descriptor tables and data inring buffer 200. A descriptor table is used to log information regardingeach data block in order to manage data in legacy ring buffer 250, L2cache 260, and preload ring buffer 230. Each data block is incrementallyindexed according to the write order, such that any two consecutive datablocks can be indexed as n and n+1. The index of each data block isassociated with the entry index of the descriptor table that describesthe information of each data block.

By way of example, four map tables are used including one for ringbuffer 200, another for legacy ring buffer 250, one for preload ringbuffer 230 and another for L2 260. In an alternative implementation,these tables are combinable so that less than four are used. Continuingthe example with four tables, a link list 500 shown in FIG. 5 is used.Link list 500 includes a ring buffer map table 501 linked to a legacyring buffer descriptor table 550, a L2 descriptor table 560, and apreload ring buffer descriptor table 530.

Memory location 570, for ease of description and understanding, is apart of legacy ring buffer 250 and has a length LEN 575. Memory location580 is part of L2 cache 260 and has a length LEN 585. Memory location590 is part of preload ring buffer 230 and has a length LEN 595. Each oftables 550, 560, 530 is linked to memory location 570, 580, 590,respectively.

One data block is associated with one descriptor, corresponding to oneentry in corresponding tables as will be described. Cur_wr_indx 510 isthe index functioning as the current write index that records latestwrite data block associated index. Cur_rd_indx 512 is the current readindex from read client. The read client uses the write order index toretrieve data from ring buffer 200. Cur_mru_indx 514 is the oldest datablock associated index in ring buffer 200. The “oldest” is defined asthe “most recent usable” (MRU) data block.

Cur_lrb_wr_indx 520 represents the latest write data block associateddescriptor index in legacy ring buffer descriptor table when that datablock is stored in legacy ring buffer. Cur_lrb_rd_indx (not shown) isthe read descriptor index when the data block is in legacy ring buffer.Cur_lrb_mru_indx 522 represents the oldest data block associated indexin legacy ring buffer descriptor table.

Cur_l2_wr_indx 524 represents the latest write data block associatedindex in L2 descriptor table when that data block is stored in L2.Cur_l2_rd_indx (not shown) represents the read index in L2 descriptortable when the data block is in L2. Cur_l2_mru_indx 526 represents theoldest data block associated index in L2 descriptor table.

Cur_plrb_wr_indx 528 represents the latest write data block associatedindex in preload ring buffer descriptor table when that data block isstored in preload ring buffer. Cur_plrb_rd_indx (not shown) representsthe read index of preload ring buffer descriptor table when the datablock is in preload ring buffer. Cur_plrb_mru_indx 546 represents theoldest data block associated index in preload ring buffer descriptortable.

Cur_lrb_wr_addr 532 represents the latest write data block associatedaddress in legacy ring buffer when it is stored in legacy ring buffer.Cur_lrb_rd_addr (not shown) represents the read address when the datablock is in legacy ring buffer. Cur_lrb_mru_addr 534 represents theoldest data block associated address in legacy ring buffer.

Cur_l2_wr_addr 536 represents the latest write data block associatedaddress when it is stored in L2. Cur_l2_rd_addr (not shown) representsthe read address when the data block is in L2. Cur_l2_mru_addr 538represents the oldest data block associated address in L2.

Cur_plrb_wr_addr 542 represents the latest write data block associatedaddress when it is stored in preload ring buffer. Cur_plrb_rd_addr (notshown) represents the read address when the data block is in preloadring buffer. Cur_plrb_mru_addr 544 represents the oldest data blockassociated address in preload ring buffer.

The read indices are not shown in FIG. 5 for purposes of clarity and areshown at least in FIG. 8. The read index to legacy ring bufferdescriptor table, L2 descriptor table, and preload ring bufferdescriptor table is determined by the retrieved DESC_INDX in ring buffermap table 501 using cur_rd_indx 512. One particular cur_rd_indxretrieves one particular DESC_INDX, either cur_lrb_rd_indx,cur_l2_rd_indx, or cur_plrb_rd_indx. The read data address is alsodetermined by the retrieved DESC_INDX, either cur_lrb_rd_addr,cur_l2_rd_addr, or cur_plrb_rd_addr.

Legacy ring buffer 250, L2 260, preload ring buffer 230 are physicallyseparately addressed. The fields of each entry of different tables aredescribed in more detail below.

The ring buffer 200 descriptor table is represented in Table 1.

TABLE 1 Ring Buffer Descriptor Table DESC_INDX: Descriptor table index:Bit “IO”: Data block in Bit “PL”: Data block for legacy ring buffer, thelegacy Bit “OBS”: Data block legacy ring buffer or external is inpreload ring ring buffer descriptor table index. is obsolete or not.L2/preload ring buffer. buffer or L2. For L2, the index of L2 descriptortable 1: obsolete 1: in legacy ring buffer 1: preload ring buffer Forpreload rig buffer, the preload Index 0: in use 0: in L2 or preload ringbuffer 0: L2 ring buffer descriptor table index. 0 1 1 0 # 1 0 1 0 # 2 00 0 # 3 1 0 0 # 4 0 1 0 # . . . . . . . . . . . . . . . n − 1 0 0 0 # n0 1 0 # n + 1 1 0 0 # . . . . . . . . . . . . . . . N 0 1 0 #

The legacy ring buffer 250 descriptor table is represented in Table 2.

TABLE 2 Legacy Ring Buffer Descriptor Table Bit “OBS”: Data block Bit“REN”: A read is P_INDX: parent table is obsolete or not. ADDR: Datablock LEN: One request issued or not for this index index, i.e. thisentry 1: obsolete address in legacy associated data 1: a read is issuedfor this index associated ring buffer Index 0: in use ring buffer blocklength 0: no previous read is issued map table index 0 1 ADDR [0] LEN[0]0 # 1 0 ADDR [1] LEN[1] 0 # 2 0 ADDR [2] LEN[2] 0 # 3 1 ADDR [3] LEN[3]0 # 4 0 ADDR [4] LEN[4] 0 # . . . . . . . . . . . . . . . . . . n − 1 0ADDR [n − 1] LEN[n − 1] 0 # n 0 ADDR [n] LEN[n] 0 # n + 1 1 ADDR [n + 1]LEN[n + 1] 0 # . . . . . . . . . . . . . . . . . . N 0 ADDR [N] LEN[N] 0#

The L2 cache 260 descriptor table is represented in Table 3.

TABLE 3 L2 Descriptor Table Bit “OWN”: Bit Read Data “REN”: block A readis ownership. Bit issued or This bit is “OBS”: not for effective onlyP_INDX: data this index when parent block is 1: a read “REN” = 1: tableobsolete is issued 1: owned by index, i.e. or LEN: for this read requestthis entry not. One index from external associated 1: ADDR: Data request0: no read client ring obsolete block associated previous 0: owned bybuffer 0: in address in data block read is preload read map table Indexuse L2 length issued controller. index 0 1 ADDR [0] LEN[0] 1 1 # 1 0ADDR [1] LEN[1] 0 0 # 2 0 ADDR [2] LEN[2] 0 0 # 3 1 ADDR [3] LEN[3] 1 1# 4 0 ADDR [4] LEN[4] 0 0 # . . . . . . . . . . . . . . . . . . . . . n− 1 0 ADDR [n − 1] LEN[n − 1] 0 0 # n 0 ADDR [n] LEN[n] 0 0 # n + 1 1ADDR [n + 1] LEN[n + 1] 1 1 # . . . . . . . . . . . . . . . . . . . . .N 0 ADDR [N] LEN[N] 0 0 #

The preload ring buffer 230 descriptor table is represented in Table 4.

TABLE 4 Preload Ring Buffer Descriptor Table Bit “OBS”: Data block Bit“REN”: A read is P_INDX: parent table is obsolete or not. LEN: Onerequest issued or not for this index index, i.e. this entry 1: obsoleteADDR: Data block associated data 1: a read is issued for this indexassociated ring buffer Index 0: in use address in L2 block length 0: noprevious read is issued map table index 0 1 ADDR [0] LEN[0] 0 # 1 0 ADDR[1] LEN[1] 0 # 2 0 ADDR [2] LEN[2] 0 # 3 1 ADDR [3] LEN[3] 0 # 4 0 ADDR[4] LEN[4] 0 # . . . . . . . . . . . . . . . . . . n − 1 0 ADDR [n − 1]LEN[n − 1] 0 # n 0 ADDR [n] LEN[n] 0 # n + 1 1 ADDR [n + 1] LEN[n + 1] 0# . . . . . . . . . . . . . . . . . . N 0 ADDR [N] LEN[N] 0 #

In Tables 1-4, “N” denotes the maximum entry index.

FIG. 6A illustrates method 600 for updating the write data associatedmanagement information of ring buffer 200. When the write controlleracknowledges each request from the write client (see FIG. 2), Tables 1-4are updated according to method 600 of FIG. 6A.

Method 600 starts with step 605 at an initial or idle state to wait fora write request. The ring buffer map table (depicted above in Table 1)is updated at step 610. A more detailed explanation of the updating ofthe ring buffer map table is included below with respect to FIG. 6B. Adecision is made, at step 620, to write to legacy ring buffer 250, L2260, or preload ring buffer 230 in accordance with FIGS. 3 and 4 and theassociated description.

Once the decision is made where the write is occurring, method 600continues to step 630 if the decision is to write to legacy ring buffer250, to step 640 if the decision is to write to L2 260, or to step 650if the decision is to write to preload ring buffer 230.

Step 630 includes updating the legacy ring buffer descriptor table(depicted above in Table 2). A more detailed explanation of the updatingof the legacy ring buffer descriptor table is included below withrespect to FIG. 6C. Once the updating is complete in step 630,cur_lrb_wr_addr is set equal to cur_lrb_wr_addr+wr_len at step 635.

Step 640 includes updating the L2 descriptor table (depicted above inTable 3). A more detailed explanation of the updating of the L2descriptor table is included below with respect to FIG. 6D. Once theupdating is complete in step 640, cur_l2_wr_addr is set equal tocur_l2_wr_addr+wr_len at step 645.

Step 650 includes updating the preload ring buffer descriptor table(depicted above in Table 4). A more detailed explanation of the updatingof the preload ring buffer descriptor table is included below withrespect to FIG. 6E. Once the updating is complete in step 650,cur_plrb_wr_addr is set equal to cur_plrb_wr_addr+wr_len at step 655.

Method 600 concludes with setting cur_wr_indx equal to cur_wr_indx+1 tocomplete the write. In an implementation, method 600 is performed againfor subsequent writes.

FIG. 6B illustrates the steps of updating the ring buffer map tablestarting at step 610. At step 612 the “IO” and “PL” bits are set basedon data block written to legacy ring buffer 250, L2 260, or preload ringbuffer 230. At step 614 “OBS” is set equal to 0 to indicate that thedata block is usable data block for reading. At step 616, the descriptorindex (DESC_INDX) is set according to the storage that is beingutilized.

For the legacy ring buffer, at step 616 the descriptor index (DESC_INDX)(cur_wr_indx) is set to cur_lrb_wr_indx, current legacy ring bufferwrite index. Additionally, an increment is added by settingcur_lrb_wr_indx=cur_lrb_wr_indx+1.

For L2, at step 616 the descriptor index (DESC_INDX)(cur_wr_indx) is setto cur_l2_wr_indx, current L2 descriptor write index. Additionally, anincrement is added by setting cur_l2_wr_indx=cur_l2_wr_indx+1.

For preload ring buffer, at step 616 the descriptor index (DESC_INDX)(cur_wr_indx) is set to cur_plrb_wr_indx, current preload ring bufferdescriptor write index. Additionally, an increment is added by settingcur_plrb_wr_indx=cur_plrb_wr_indx+1.

FIG. 6C illustrates the steps of updating the legacy ring bufferdescriptor table starting at step 630. At step 631, the “OBS’ bit is setto 0 to indicate that the data block is usable for reading. At step 632,the “ADDR” is set to log current write address. For example,ADDR[cur_lrb_wr_indx]=cur_lrb_wr_addr where cur_lrb_wr_indx is thecurrent legacy ring buffer write index and cur_lrb_wr_addr is thecurrent legacy ring buffer data block write address.

At step 633, “LEN” is set to record the current write data block lengthwhere LEN[cur_lrb_wr_indx] is equal to wr_len and wr_len is the writedata length. At step 634, “REN” is set to 0 to indicate entry is notread by read client at present. At step 636, “P_INDX” is set to indicatethe legacy ring buffer in the associated ring buffer map table index(e.g., cur_wr_indx).

FIG. 6D illustrates the steps of updating the L2 descriptor tablestarting at step 640. At step 641, the “OBS’ bit is set to 0 to indicatethat the data block is usable for reading. At step 642, the “ADDR” isset to log current write address. For example,ADDR[cur_l2_wr_indx]=cur_l2_wr_addr where cur_l2_wr_indx is the currentL2 write index and cur_l2_wr_addr is the current L2 ring buffer datablock write address.

At step 643, “LEN” is set to record the current write data block lengthwhere LEN[cur_l2_wr_indx] is equal to wr_len and wr_len is the writedata length. At step 644, “REN” is set to 0 to indicate entry is notread by read client at present. At step 646, “P_INDX” is set to indicatethe L2 in the associated ring buffer map table index (e.g.,cur_wr_indx). At step 647, “OWN” is set to 1 to indicate that it isundefined since “REN”=0.

FIG. 6E illustrates the steps of updating the preload ring bufferdescriptor table starting at step 650. At step 651, the “OBS’ bit is setto 0 to indicate that the data block is usable for reading. At step 652,the “ADDR” is set to log current write address. For example,ADDR[cur_plrb_wr_indx]=cur_plrb_wr_addr where cur_plrb_wr_indx is thecurrent preload ring buffer write index and cur_plrb_wr_addr is thecurrent preload ring buffer data block write address.

At step 653, “LEN” is set to record the current write data block lengthwhere LEN[cur_plrb_wr_indx] is equal to wr_len and wr_len is the writedata length. At step 654, “REN” is set to 0 to indicate entry is notread by read client at present. At step 656, “P_INDX” is set to indicatethe preload ring buffer in the associated ring buffer map table index,for example, cur_wr_indx.

FIG. 7 illustrates management information update for write data of thering buffer 200. FIG. 7 depicts the three possible write scenarios ofwriting to legacy ring buffer descriptor table 550, to L2 descriptortable 560, and to the preload ring buffer descriptor table 530. Whileonly a single scenario occurs at one time, FIG. 7 illustrates all threepossibilities. In writing data, a write index, cur_wr_indx 710, pointsto a portion of ring buffer map table 501, resulting from animplementation where step 616 of FIG. 6B sets the pointer for the writeindex. If the write is to the legacy ring buffer 250, write index 710 ais applicable. If the write is to L2 260, write index 710 b applies. Ifthe write is to the preload ring buffer 230, write index 710 c applies.The read index, cur_rd_indx, 720 references another point on ring buffermap table 501.

If the legacy ring buffer 250 is determined to be the location of thewrite, cur_wr_indx 710 a is set equal to cur_lrb_wr_indx. After settingcur_wr_indx 710 a, as a result of cur_wr_indx being used as an index ofDESC_INDX, cur_lrb_wr_indx is incremented by 1 as a subsequent writeindex using cur_wr_indx=cur_wr_indx+1 andcur_lrb_wr_indx=cur_lrb_wr_indx+1. Using the pointer for cur_lrb_wr_indx760 a (step 616 of FIG. 6B and steps 630-636 of FIG. 6C), the legacyring buffer descriptor table 550 is accessed. After the write, thecurrent write index is reset to cur_wr_indx in order for subsequentwrites to occur.

If L2 260 is determined to be the location of the write, cur_wr_indx 710b is set equal to cur_l2_wr_indx. After setting cur_wr_indx 710 b, as aresult of cur_wr_indx being used as an index of DESC_INDX,cur_l2_wr_indx is incremented by 1 as a subsequent write index usingcur_wr_indx=cur_wr_indx+1 and cur_l2_wr_indx=cur_l2_wr_indx+1. Using thepointer for cur_l2_wr_indx 760 b (step 616 of FIG. 6B and steps 641-647of FIG. 6D), L2 descriptor table 560 is accessed. After the write, thecurrent write index is reset to cur_wr_indx in order for subsequentwrites to occur.

If the preload ring buffer 230 is determined to be the location of thewrite, cur_wr_indx 710 c is set equal to cur_plrb_wr_indx. After settingcur_wr_indx 710 c, as a result of cur_wr_indx being used as an index ofDESC_INDX, cur_plrb_wr_indx is incremented by 1 as a subsequent writeindex using cur_wr_indx=cur_wr_indx+1 andcur_plrb_wr_indx=cur_plrb_wr_indx+1. Using the pointer forcur_plrb_wr_indx 760 c (step 616 of FIG. 6B and steps 650-656 of FIG.6E), the preload ring buffer descriptor table 530 is accessed. After thewrite, the current write index is reset to cur_wr_indx in order forsubsequent writes to occur.

FIG. 8 illustrates the read control arbitor 240 for the ring buffer ofFIG. 2. There are two sources of read request for read control arbitor240. A read request either comes from a read client 810 or there is apreload read request 820. Read control arbitor 240 arbitrates betweenthese requests to manage the data. Read requests are sent from readcontrol arbitor 240 to the legacy ring buffer via read request to legacyring buffer 850, to L2 via read request to L2 860, and to preload ringbuffer via read request to preload ring buffer 830. Data is returned toread control arbitor 240 from the legacy ring buffer via legacy ringbuffer read data return 855, from L2 via L2 read data return 865, andfrom preload ring buffer via preload ring buffer read data return 835.

FIG. 9 illustrates a read control arbitration finite state machine (FSM)that is used to arbitrate the reads. FSM 900 includes an initial statedenoted as init_state 910. The state where read request from read clientis acknowledged is denoted as rd_state 920. The state where preloadcondition is met, the preload is initiated with read controller requestis acknowledged and denoted as pl_rd_state 930. The state where readdata is returned from L2 is denoted as l2_rdat_return_state 940. Thestate where read data is returned from legacy ring buffer is denoted aslrb_rdat_return_state 950. The state where read data is return frompreload ring buffer is denoted as plrb_rdat_return_state 960.

From init_state 910 FSM 900 moves to any one of the other statesrd_state 920, pl_rd_state 930, l2_rdat_return_state 940,lrb_rdat_return_state 950, and plrb_rdat_return_state 960.

A read request from a read client causes rd_state 920 to be selected asthe state until a read request from read client is issued causing thestate to return to init_state 910. The selection of a preload controllerread request causes pl_rd_state 930 to be selected as the state until apreload controller read request is issued causing the state to return toinit_state 910. The selection of a L2 read data causesl2_rdat_return_state 940 to be selected as the state until a L2 readdata return is completed causing the state to return to init_state 910.The selection of a legacy ring buffer read data causeslrb_rdat_return_state 950 to be selected as the state until a legacyring buffer data return is completed causing the state to return toinit_state 910. The selection of a preload ring buffer read data causesplrb_rdat_return_state 960 to be selected as the state until a preloadring buffer read data return is completed causing the state to return toinit_state 910. FSM 900 controls which client has exclusive access tothe tables. Each time an access occurs, the access finishes atomically.In an implementation, init_state 910 uses a round-robin selector toselect which request is to be acknowledged and acted upon.

FIG. 10 illustrates the method 1000 of operations in state rd_state 920of FSM 900 of FIG. 9. Method 1000 begins at step 1005 with an initial oridle state to wait for a read request. At step 1010, a decision aboutentering rd_state 920 occurs. If the state is not entered, method 1000loops back to step 1005. If rd_state 920 is entered, then at step 1015the cur_rd_indx is used to query ring buffer map table to extract OBS,IO, PL, and DESC_INDX where OBS can be used to examine if the read isacceptable. After these variables are extracted, a determination ifIO[cur_rd_indx]=1 is made at step 1020. If this determination ispositive, cur_lrb_rd_indx=DESC_INDX[cur_rd_indx] at step 1025. Afterstep 1025, at step 1030 a determination of the value ofREN[cur_lrb_rd_indx] is compared to 1. If this value is not 1, method1000 sets OWN[cur_lrb_rd_indx]=1 and exits rd_state at step 1032returning to step 1005. If the determination is that the value is 1,then at step 1035 OWN[cur_lrb_rd_indx] is set to 1 andREN[cur_lrb_rd_indx] is set to 1. At step 1040, ADDR[cur_lrb_rd_indx]and LEN[cur_lrb_rd_indx] are used to issue read request to legacy ringbuffer 250 and exit rd_state 920.

If the determination at step 1020 is negative, a determination ofwhether PL[cur_rd_indx]=1 is made at step 1045. If this determination isnegative, then cur_l2_rd_indx is set equal to DESC_INDX[cur_rd_indx] atstep 1050. At step 1055 a determination is made as to whetherREN[cur_l2_rd_indx] equals 1. If that determination is positive, thenOWN[cur_l2_rd_indx] is set to 1 and rd_state 920 is exited at step 1060.If the determination at step 1055 is negative OWN[cur_l2_rd_indx] andREN[cur_l2_rd_indx] are each set to 1 at step 1065. At step 1070,ADDR[cur_l2_rd_indx] and LEN[cur_l2_rd_indx] are used to issue a readrequest to L2 260 and rd_state 920 is exited.

If the determination at step 1045 is positive, then at step 1075cur_plrb_rd_indx is set to DESC_INDX[cur_rd_indx]. At step 1080 adetermination of whether OWN[cur_plrb_rd_indx] is equal to 1. If thedetermination is positive, then OWN[cur_plrb_rd_indx] is set to 1 andrd_state 920 is exited at step 1085. If the determination at step 1080is negative, OWN[cur_plrb_rd_indx] and REN[cur_plrb_rd_indx] are setequal to 1 at step 1090. At step 1095, ADDR[cur_lrb_rd_indx] andLEN[cur_lrb_rd_indx] are used to issue read request to legacy ringbuffer 250 and rd_state 920 is exited.

FIG. 11 illustrates management information extraction and update inrd_state 920. FIG. 11 depicts the three possible read scenarios ofreading from legacy ring buffer descriptor table 550, to L2 descriptortable 560, and to the preload ring buffer descriptor table 530. Whileonly a single scenario occurs at one time, FIG. 11 is shown toillustrate all three possibilities. In reading data to satisfy a readrequest, the data is read from one of three locations within the ringbuffer as described herein. In reading data a write index, cur_wr_indx1110 points to a portion of ring buffer map table 501. The read index,cur_rd_indx 1120 references another point on ring buffer map table 501.In the case where the read is from the legacy ring buffer 250 (step 1025from FIG. 10), read index 1120 a applies. If the read is from L2 260(step 1050 from FIG. 10), read index 1120 b applies. If the read is fromthe preload ring buffer 230 (step 1075 from FIG. 10), read index 1120 capplies.

If the legacy ring buffer 250 is determined to be the location where thedata to be read is located, cur_rd_indx 1120 a is set equal tocur_lrb_rd_indx and using the pointer for cur_lrb_rd_indx 1160 a, thelegacy ring buffer descriptor table 550 is accessed.

If L2 260 is determined to be the location where the data to be read islocated, cur_rd_indx 1120 b is set equal to cur_l2_rd_indx and using thepointer for cur_l2_rd_indx 1160 b, L2 descriptor table 560 is accessed.

If the preload ring buffer 230 is determined to be the location wherethe data to be read is located, cur_rd_indx 1120 c is set equal tocur_plrb_rd_indx and using the pointer for cur_plrb_rd_indx 1160 c thepreload ring buffer descriptor table 530 is accessed.

FIG. 12 illustrates the operations in state pl_rd_state 930 of the FSM900 of FIG. 9. Method 1200 begins at step 1205 with an initial or idlestate to wait for a read request. At step 1210, a decision aboutentering pl_rd_state 930 occurs. If the state is not entered, method1200 loops back to step 1205. If pl_rd_state 930 is entered, then atstep 1215 the cur_l2_rd_indx=cur_l2_mru_indx is used to extract L2descriptor table information. At step 1220 a determination is made ifREN[cur_l2_rd_indx] is equal to 1. If the determination is positive,OWN[cur_l2_rd_indx] is set to 1 and pl_rd_state 930 is exited at step1225. If the determination is negative, OWN[cur_l2_rd_indx] is set to 0and REN[cur_l2_rd_indx] is set to 1 at step 1230. At step 1235,ADDR[cur_l2_rd_indx] and LEN[cur_l2_rd_indx] are used to issue a readrequest to L2 260 and pl_rd_state 930 is exited.

FIG. 13 illustrates management information extraction and update 1300 inpl_rd_state 930. FIG. 13 illustrates cur_wr_indx 1310 indexing the ringbuffer map table 501. Cur_mru_indx 1340 also indexes the ring buffer maptable 501. As pl_rd_state 930 utilizes L2 260, L2 descriptor table 560is indexed from ring buffer map table 1340 using cur_l2_mru_indx 1360.Once cur_l2_mru_infix 1360 is calculated using cur_mr_indx 1340 orcur_rd_indx (not shown).

FIG. 14 illustrates the operations in state lrb_rdat_return_state 950 ofthe FSM 900 of FIG. 9. Method 1400 begins at step 1405 with an initialor idle state to wait for a read data return from legacy ring buffer250. At step 1410, a decision about entering lrb_rdat_return_state 950occurs. If the state is not entered, method 1400 loops back to step1405. If lrb_rdat_return_state 950 is entered, then at step 1415 thereturn data tag is used to infer the return data associatedcur_lrb_rd_indx and cur_rd_indx is set equal to P_INDX[cur_lrb_rd_indx]from the legacy ring buffer descriptor table. At step 1415,OBS[cur_rd_indx] and OBS[cur_lrd_rd_indx] is extracted from the ringbuffer map table and the legacy ring buffer descriptor table,respectively. OBS[cur_rd_indx] is set equal to 1 in the ring buffer maptable and OBS[cur_lrd_rd_indx] is set equal to 1 in the legacy ringbuffer descriptor table. At step 1420, cur_lrb_mru_indx and cur_mru_indxare updated, when necessary, with cur_lrb_mru_indx to obtaincur_lrb_rd_addr=ADDR[cur_lrb_mru_indx] and then cur_lrb_addr is used forlegacy ring buffer free space calculation. Once all of the read data iswritten to the read agent, lrb_rdat_return_state 950 is exited.

For each read data return to read client, a calculation of the mostrecent usable (MRU) index is performed to expose the free space ofcorresponding ring buffers. FIG. 15 illustrates the ring buffer 200 mostrecent usable index calculation 1500. Calculation 1500 begins at step1505 with an initial or idle state to wait for a read request. At step1510, a decision on whether to update cur_mru_indx is performed. If thisdetermination is negative, calculation 1500 returns to step 1505. If thedetermination is positive, at step 1515 a determination is made as towhether cur_rd_indx=cur_mru_indx. If this determination is negative,calculation 1500 returns to step 1505. If the determination is positive,at step 1520 a determination is made as to whethercur_mru_indx=cur_wr_indx and cur_mru_indx is set equal tocur_mru_index+1 at step 1530. If the determination at step 1520 isnegative, calculation 1500 returns to step 1505. If the determination atstep 1520 is positive, at step 1525 a determination is made as towhether OBS[cur_mru_indx] equals 1. If the determination at step 1525 isnegative, calculation 1500 returns to step 1505. If the determination atstep 1525 is positive, at step 1530, cur_mru_indx is set equal tocur_mru_index+1.

FIG. 16 illustrates the legacy ring buffer 250 most recent usable indexcalculation 1600. Calculation 1600 begins at step 1605 with an initialor idle state to wait for a read request. At step 1610, a decision onwhether to update cur_lrb_mru_indx is performed. If this determinationis negative, calculation 1600 returns to step 1605. If the determinationis positive, at step 1615 a determination is made as to whethercur_lrb_rd_indx=cur_lrb_mru_infix. If this determination is negative,calculation 1600 returns to step 1605. If the determination is positive,at step 1620 a determination is made as to whethercur_lrb_mru_indx=cur_lrb_wr_indx and cur_lrb_mru_indx is set equal tocur_lrb_mru_index+1 at step 1630. If the determination at step 1620 isnegative, calculation 1600 returns to step 1605. If the determination atstep 1620 is positive, at step 1625 a determination is made as towhether OBS[cur_lrb_mru_indx] equals 1. If the determination at step1625 is negative, calculation 1600 returns to step 1605. If thedetermination at step 1625 is positive, at step 1560, cur_lrb_mru_indxis set equal to cur_lrb_mru_index+1.

Cur_lrb_mru_indx is used to retrieve associated data block address inlegacy ring buffer 250 with cur_lrb_mru_rd_addr=ADDR[cur_lrb_mru_indx]and combining cur_lrb_wr_addr applied to determine if legacy ring buffer250 has free space to fill.

FIG. 17 illustrates an example 1700 where current read index 1720 isbetween current write index 1710 and most recent usable index 1740leaving cur_lrb_mru_indx 1710 unchanged. In an implementation, example1700 may operate as described in one of FIGS. 14-16.

FIG. 18 illustrates the operations in state plrb_rdat_return_state 960of the FSM 900 of FIG. 9. Method 1800 begins at step 1805 with aninitial or idle state to wait for a read data return from preload ringbuffer 230. At step 1810, a decision about enteringplrb_rdat_return_state 960 occurs. If the state is not entered, method1800 loops back to step 1805. If plrb_rdat_return_state 960 is entered,then at step 1815 the return data tag is used to infer the return dataassociated cur_plrb_rd_indx and cur_rd_indx is set equal toP_INDX[cur_plrb_rd_indx] from the preload ring buffer descriptor table.At step 1815, OBS[cur_rd_indx] and OBS[cur_plrb_rd_indx] is extractedfrom the ring buffer map table and the preload ring buffer descriptortable, respectively. OBS[cur_rd_indx] is set equal to 1 in the ringbuffer map table and OBS[cur_plrb_rd_indx] is set equal to 1 in thepreload ring buffer descriptor table. At step 1820, cur_plrb_mru_indxand cur_mru_indx are updated with cur_plrb_mru_indx andcur_plrb_rd_addr=ADDR[cur_plrb_mru_indx] is used for preload ring bufferfree space calculation. Once all of the read data is written to the readagent, plrb_rdat_return_state 960 is exited.

FIG. 19 illustrates the preload ring buffer 230 most recent usable indexcalculation 1900. Calculation 1900 begins at step with an initial oridle state to wait for a read request. At step 1910, a decision onwhether to update cur_plrb_mru_indx is performed. If this determinationis negative, calculation 1900 returns to step 1905. If the determinationis positive, at step 1915 a determination is made as to whethercur_plrb_rd_indx=cur_plrb_mru_indx. If this determination is negative,calculation 1900 returns to step 1905. If the determination is positive,at step 1920 a determination is made as to whethercur_plrb_mru_indx=cur_plrb_wr_indx and cur_plrb_mru_indx is set equal tocur_plrb_mru_indx+1 at step 1930. If the determination at step 1920 isnegative, calculation 1900 returns to step 1905. If the determination atstep 1920 is positive, at step 1925 a determination is made as towhether OBS[cur_plrb_mru_indx] equals 1. If the determination at step1925 is negative, calculation 1900 returns to step 1905. If thedetermination at step 1925 is positive, at step 1930, cur_plrb_mru_indxis set equal to cur_plrb_mru_indx+1.

Cur_plrb_mru_indx is used to retrieve associated data block address inpreload ring buffer 230 withcur_plrb_mru_rd_addr=ADDR[cur_plrb_mru_indx] and combiningcur_plrb_wr_addr applied to determine if preload ring buffer 230 hasfree space to fill.

FIG. 20 illustrates an example 2000 where current read index 2020 equalsthe most recent usable index 2040 skipping all obsolete entries 2030 upto current write index 2010. In an implementation, example 2000 mayoperate as described in one of FIGS. 18-19.

FIG. 21 illustrates the operations in state l2_rdat_return_state 940 ofthe FSM 900 of FIG. 9. Method 2100 begins at step 2105 with an initialor idle state to wait for a read data return from L2 260. At step 2110,a decision about entering l2_rdat_return_state 940 occurs. If the stateis not entered, method 2100 loops back to step 2105. Ifl2_rdat_return_state 940 is entered, then at step 2115 the return datatag is used to infer the return data associated cur_l2_rd_indx andcur_rd_indx is set equal to P_INDX[cur_l2_rd_indx] from the L2descriptor table. At step 2120, a determination is made as to whetherOWN[cur_l2_rd_indx]=1. If the determination at step 2120 is positive, atstep 2125, OBS[cur_rd_indx] and OBS[cur_l2_rd_indx] is extracted fromthe ring buffer map table and the L2 descriptor table, respectively.OBS[cur_rd_indx] is set equal to 1 in the ring buffer map table andOBS[cur_l2_rd_indx] is set equal to 1 in the L2 descriptor table. Atstep 2130, cur_l2_mru_indx and cur_mru_indx are updated withcur_l2_mru_indx and cur_l2_rd_addr=ADDR[cur_l2_mru_indx] is used for L2free space calculation. Once all of the read data is written to the readagent, l2_rdat_return_state 940 is exited.

If step 2120 is negative, step 2135 and step 2140 is performed prior toperforming step 2130. Step 2135 setsDESC_INDX[cur_rd_indx]=cur_plrb_wr_indx and PL[cur_rd_indx]=1 in thering buffer map table and sets OBS[cur_l2_rd_indx]=1 andREN[cur_l2_rd_indx]=0 in the L2 descriptor table. Preload ring buffer230 is updated as described in FIG. 6A steps 650, 655 and FIG. 6E. Step2140 sets cur_plrb_wr_indx=cur_plrb_wr_indx+1.

FIG. 22 illustrates the L2 260 most recent usable index calculation2200. Calculation 2200 begins at step 2205 with an initial or idle stateto wait for a read request. At step 2210, a decision on whether toupdate cur_l2_mru_indx is performed. If this determination is negative,calculation 2200 returns to step 2205. If the determination is positive,at step 2215 a determination is made as to whethercur_l2_rd_indx=cur_l2_mru_indx. If this determination is negative,calculation 2200 returns to step 2205. If the determination is positive,at step 2220 a determination is made as to whethercur_l2_mru_indx=cur_l2_wr_indx and cur_l2_mru_indx is set equal tocur_l2_mru_indx+1 at step 2230. If the determination at step 2220 isnegative, calculation 2200 returns to step 2205. If the determination atstep 2220 is positive, at step 2225 a determination is made as towhether OBS[cur_l2_mru_indx] equals 1. If the determination at step 2225is negative, calculation 2200 returns to step 2205. If the determinationat step 2225 is positive, at step 2230, cur_l2_mru_indx is set equal tocur_l2_mru_indx+1.

Cur_l2_mru_indx is used to retrieve associated data block address in L2260 with cur_l2_mru_rd_addr=ADDR[cur_l2_mru_indx] and combiningcur_l2_wr_addr applied to determine if L2 260 has free space to fill.

FIG. 23 illustrates an example 2300 where current read index 2320 equalsthe most recent usable index 2340 skipping all obsolete entries 2330 upto some usable entry. In an implementation, example 2300 may operate asdescribed in one of FIGS. 21-22.

The present invention supports random read (de-allocation) of data andoutstanding read (de-allocation) from read client. The present inventionoperates with write data that is sequential so that the write data canbe written to ring buffer in incoming order. The present inventionoperates with a read client using the write order index to retrieve datafrom ring buffer. Further, the order to read/write internal on-chipbuffer ring or external L2/off-chip memory is maintained and the readreturn order as well. The read can be associated with de-allocation, oralternatively, “de-allocate” operations may be substituted for “read”operations. A “read but not de-allocate” operation may also be utilizedwhere the read operation is performed, but the associated data block isnot de-allocated. The above description utilizes descriptor tables ofsufficient size to describe corresponding ring buffers.

It should be understood that many variations are possible based on thedisclosure herein. Although features and elements are described above inparticular combinations, each feature or element may be used alonewithout the other features and elements or in various combinations withor without other features and elements.

The methods provided may be implemented in a general purpose computer, aprocessor, or a processor core. Suitable processors include, by way ofexample, a general purpose processor, a special purpose processor, aconventional processor, a digital signal processor (DSP), a plurality ofmicroprocessors, one or more microprocessors in association with a DSPcore, a controller, a microcontroller, Application Specific IntegratedCircuits (ASICs), Field Programmable Gate Arrays (FPGAs) circuits, anyother type of integrated circuit (IC), and/or a state machine. Suchprocessors may be manufactured by configuring a manufacturing processusing the results of processed hardware description language (HDL)instructions and other intermediary data including netlists (suchinstructions capable of being stored on a computer readable media). Theresults of such processing may be maskworks that are then used in asemiconductor manufacturing process to manufacture a processor whichimplements aspects of the embodiments.

The methods or flow charts provided herein may be implemented in acomputer program, software, or firmware incorporated in a non-transitorycomputer-readable storage medium for execution by a general purposecomputer or a processor. Examples of non-transitory computer-readablestorage mediums include a read only memory (ROM), a random access memory(RAM), a register, cache memory, semiconductor memory devices, magneticmedia such as internal hard disks and removable disks, magneto-opticalmedia, and optical media such as CD-ROM disks, and digital versatiledisks (DVDs).

What is claimed is:
 1. A system for managing data in a ring buffer, saidsystem comprising: a legacy ring buffer resident on a chip with aprocessor and configured to store data based on writes to the ringbuffer; a supplemental buffer for storing data based on writes to thering buffer; a preload ring buffer resident on the chip and capable ofreceiving preload data from the supplemental buffer; a write controllerthat selects between the legacy ring buffer and the supplemental bufferas a write location for writing data that is write requested by a writeclient of the ring buffer; and a read controller that controls a returnof the ring buffer data to a read client pursuant to a read request tothe ring buffer.
 2. The system of claim 1 wherein if the legacy ringbuffer is not full and the supplemental buffer is empty, the writecontroller selects to the legacy ring buffer on a write request.
 3. Thesystem of claim 2 wherein the writing to the legacy ring buffer occurson subsequent write requests until the legacy ring buffer is full. 4.The system of claim 1 wherein if the legacy ring buffer is full and thesupplemental buffer is not full, the write controller selects thesupplemental buffer on a write request.
 5. The system of claim 1 whereinif the legacy ring buffer is full and there is no data in thesupplemental buffer, the write controller selects the preload ringbuffer on a write request.
 6. The system of claim 1 wherein upon receiptof the read request, the read controller examines the legacy ring bufferand preload ring buffer to satisfy the read request.
 7. The system ofclaim 6 wherein if the legacy ring buffer contains the data to be readin the read request, the data is supplied from the legacy ring buffer tosatisfy the read request.
 8. The system of claim 6 wherein if thepreload ring buffer contains the data to be read in the read request,the data is supplied from the preload ring buffer to satisfy the readrequest.
 9. The system of claim 6 wherein if the legacy ring buffer andpreload ring buffer do not contain the data to be read in the readrequest, the read request is sent to the supplemental buffer to fetchthe data.
 10. The system of claim 9 wherein the read data is returned tothe read client from the supplemental buffer.
 11. The system of claim 1wherein the read controller determines that preload ring buffer is notfull and there is data stored in the supplemental buffer, the readcontroller loads an oldest usable data from the supplemental buffer tothe preload ring buffer.
 12. The system of claim 1 wherein thesupplemental buffer is an off-chip memory.
 13. The system of claim 12wherein the off-chip memory is a DDR.
 14. The system of claim 1 whereinthe supplemental buffer is an L2 cache.
 15. A method for writing data ina ring buffer, the ring buffer including a legacy ring buffer residenton a chip with a processor and configured to store data based on writesto the ring buffer, a supplemental buffer for storing data based onwrites to the ring buffer and a preload ring buffer resident on the chipand capable of receiving preload data from the supplemental buffer, themethod comprising: receiving a write request from a write client towrite data to the ring buffer; and writing the data to the legacy ringbuffer on the write request, if the legacy ring buffer is not full andthe supplemental buffer is empty, writing data to the supplementalbuffer on the write request, if the legacy ring buffer is full and thesupplemental buffer is not full, and writing the data to preload ringbuffer on the write request, if the legacy ring buffer is full and thereis no data in the supplemental buffer.
 16. The method of claim 15wherein the writing to the legacy ring buffer occurs on subsequent writerequests until the legacy ring buffer is full.
 17. The method of claim15 wherein the supplemental buffer is an L2 cache.
 18. A method forreading data in a ring buffer, the ring buffer including a legacy ringbuffer resident on a chip with a processor and configured to store databased on writes to the ring buffer, a supplemental buffer for storingdata based on writes to the ring buffer and a preload ring bufferresident on the chip and capable of receiving preload data from thesupplemental buffer, the method comprising: examining the legacy ringbuffer and preload ring buffer to satisfy a read request for the data;and if the legacy ring buffer contains the data to be read in the readrequest, supplying the data from the legacy ring buffer to satisfy theread request, if the preload ring buffer contains the data to be read inthe read request, supplying the data from the preload ring buffer tosatisfy the read request, and if the legacy ring buffer and preload ringbuffer do not contain the data to be read in the read request, sendingthe data read request to the supplemental buffer to fetch the data,wherein the read data is returned to a read client from the supplementalbuffer.
 19. The method of claim 18, wherein further comprising loadingthe oldest usable data from the supplemental buffer to the preload ringbuffer, after determining that the preload ring buffer is not full andthere is data stored in the supplemental buffer.
 20. The method of claim19 wherein the supplemental buffer is a memory not resident on the chip.